1. Field of the Invention
The present invention relates to a coplanar antenna unit and a coplanar antenna, in particular to a coplanar antenna unit of a leaky-wave antenna and a coplanar antenna of a leaky-wave antenna.
2. Description of the Related Art
Leaky-wave antenna has a significant contribution to the development of wireless systems. Antenna capable of integrating a composite right/left-handed (CRLH) material with wireless communications is one of the popular research subjects in recent years. Therefore, a composite right/left-handed (CRLH) structure is one of the best techniques used in these popular applications. At present, methods of designing a leaky-wave antenna are mainly divided into the following types:
1. Using a periodic structure: A periodic structure such as a dielectric grid, a metal plate grid and a groove grid of a metal plate is formed by a space harmonic wave produced by a periodical effect.
2. Using an opening waveguide: An opening waveguide such as a corrugated waveguide, a non-radiation medium waveguide and a micro strip is operated at a high-order mode to achieve the functions of a leaky-wave antenna.
3. Integrating with a meta-material: Both radiation region and waveguide region are provided in a general mode, such that when the operating frequency falls within the radiation region, a leaky-wave antenna is achieved.
Although the prior art can achieve the effect of a leaky-wave antenna, most energies in the structure are leaked to the space to achieve high gain and antenna efficiency. To achieve this effect, manufacturers use a leaky-wave antenna made of a periodic structure, an opening waveguide or a meta-material with a sufficient length to transmit a large portion of energies into the space. To cope with the mainstream of miniaturization and meet the requirements of an integrated communication system, it is very important to minimize the volume of the leaky-wave antenna.